Orthogonal. Having ADHD doesn't imply a desire to be outside playing. It's a disorder of motivation, not a disorder of focus—an inability to practice , and sometimes to concentrate ; but not an inability to think, or to enjoy thinking. Personally, in my childhood, I liked math and science. I had (and still have) ADHD, which made that hard, but I struggled through, because that was my passion. Medication (which I didn…
I would further polish your desription - and call it a disorder of mismatched motivation. People with ADHD can motivate just fine on things that stimulate them - and have even reported 'hyperfocus', a trance-like state of emersion in something. The problem is things that are not stimulating become very challanging or even impossible. This is why bills, appointment, rules, and chores can be so difficult for ADHD peopl…
To put it another way: some things in life are a hassle (or a "schlep", in pg's phrasing[1]). The more motivation you have, the less this matters. The less motivation you have, the more of a problem a thing being a "hassle" will be. When you have chronically-low motivation, you avoid "hassles" as a rule, to the point that you stop even being able to lead your mind down potential avenues of thought that involve "hassles."
If you want a fictional example of what having ADHD really tends to look like, it's not Calvin of C&H, it's Shikamaru from Naruto[2].
This model, by the way, has all sorts of consequences outside of just ADHD. When people are "too hungry to decide what to eat"—that's because hunger depletes motivation, and decisions are fundamentally hassles. The hungrier you get, the less motivation you can tap to "just" decide. (You can force yourself to decide, or trick yourself into deciding, but you can't "just" decide.)
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[1] http://paulgraham.com/schlep.html
[2] Yui from K-On is also a striking example. That show's entire theme, actually, is essentially "how to succeed in life despite having ADHD", which is a real surprise for something so fluffy.